The present invention relates generally to the art of welding power supplies. More specifically, it relates to welding power supplies with feedback selected from more than one source.
There are many types of welding systems used for a variety of applications. Typical prior art welding systems include a power supply, such as phase control, inverter and converter based power supplies, and a controller that controls the output of the power supply.
Prior art controllers use a number of fedback parameters, including output current and output voltage. Output voltage, as used herein, includes the output voltage of a power supply, either at the power supply, or at a remote location such as the workpiece.
When output voltage is the fedback parameter it is known in the prior art to feedback either power supply voltage or voltage from sense leads connected to the workpiece or bench, and the wire feed motor. Power supply voltage, as used herein, includes output voltage in or near the power supply, such as on the output studs. Voltage sense lead, as used herein, includes one or more leads used to sense output voltage remotely from the power supply, such as at the workpiece and/or the wire feeder.
The power supply voltage may differ from a sense lead voltage because of losses in the welding cable. Often, the power supply voltage is sufficient to control the power supply. Other times a more accurate voltage feedback is desired, and sense leads are used.
Sense leads typically connect to a specially designated sensor on the welding power supply. The negative voltage sense lead is typically clamped or clipped onto the workpiece or workbench, and the positive voltage sense lead is typically connected to the wire feed motor. The sense leads often lay on the ground between the welding power supply and the workpiece.
Users can select whether power supply voltage or sense lead voltage is used for feedback. Alternatively, some inverter based prior art welding systems, such as the Miller Maxtron(trademark), automatically select the source of feedback. Specifically, the feedback from both sources are ORED together such that if a valid output voltage feedback is on the sense lead, then the sense lead voltage is used as the feedback control. Alternatively, if there is no valid output voltage feedback on the sense lead, then the welding power supply voltage is used as the feedback voltage. Valid output voltage feedback, as used herein, includes signals indicative of output voltages provide during a weld or open circuit condition.
Because the Maxtron(trademark) continuously monitors of the sense lead voltage and the power supply voltage the source of the feedback can change during a welding process. This may be necessary if the sense lead feedback is interrupted. The sense lead feedback may be interrupted because the sense lead can be inadvertently removed from the workpiece, or the lead itself can be damaged, such as by being run over.
However, the user does not know the source of feedback has changed, and this may adversely affect the welding process. Because the user does not know the source of feedback has changed, the user does not have the opportunity to reconnect or replace the sense lead.
Accordingly, a welding power supply that receives feedback from multiple sources and that the selects the source of feedback, and notifies the user of the source selected and/or a change in the source of feedback, is desirable. Preferably, such a welding power supply can be used with a phase control power supply.
According to a first aspect of the invention a welding system includes a power supply and a controller. The power supply has at least one control input and a power output. The controller has at least one control output connected to the controller. It also has two feedback inputs connected to two sources of feedback of a welding parameter. A dynamic feedback source selector is connected to the two sources of feedback. A feedback source user indicator is connected to and responsive to the dynamic feedback source selector.
A second aspect of the invention is a method of welding including providing and controlling welding power. Feedback of a welding parameter is sensed from two sources. The source to be used to control the power supply is dynamically selected. Also, and indication is provided to the user if the source of feedback selected changes.
The sources of feedback are voltage feedback in one embodiment. One source is power supply voltage, and the other voltage sense lead in various embodiments.
The dynamic feedback source selector includes software that selects the power supply voltage if the sense lead voltage is not valid feedback, and selects the sense lead voltage if it is valid feedback in yet another embodiment.
The controller includes a microprocessor, and at least a part of the dynamic feedback source selector is implemented with software and may include noise filtering software in other embodiments.
The feedback source user indicator includes software that activates a user indicator at the completion of a weld process, if the selection changed during the weld process in another alternative.
The power supply is a phase controlled power supply in another embodiment.
According to a third aspect of the invention a system for welding includes a phase controlled power supply a that has a control input and a power output. A microprocessor based controller provides a control output to the power supply. Two feedback inputs are connected to two sources of feedback of a welding parameter. A software based dynamic feedback source selector includes noise filtering.
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.